Eventhough both are almost identical ( same brand, multiview & uses same drivers ? )

Would something blow up if I did try both ?

Actually, they're more different than you think. The FirePro 2460 is a DX11 video card where as the FireMV 2260 is a DX10.1 video card (see here). You could try using both video cards at the same time but you'd be wasting your time. I wouldn't do it if I were you though. I doubt there would be any risk of hardware damage but I'm not 100% sure. But as they say, it's better to be safe than sorry.

Yes they will both work together (in the same motherboard)Just make sure to place the 2460 on the blue pcie slot, and the 2260 not in the next black one,but the one with the light blue clip (3rd slot)That way they will share lane bandwidth and have seamlessly no lag(has nothing to do with DX11, crossfire, etc.... )No need to download drivers, as BOTH cards use the same one you already have installed.

There isn't much in the way of advantages of running a second video card in non SLI/XFire scenarios, but of course with most things; there are exceptions. Some people use one card for Gaming and the other for Productivity (ex. CAD). Some people use it primarily to pump out a 3rd (in your case - 4th) Monitor as most singular Video Cards will not run 3 Monitors at all (let alone more than 3).

Keep in mind that you will not be playing a Game on all 4 Monitors since the Game can only 'converse' with 1 Card at a time, and even if it somehow could talk to both you'd have an issue with Syncing everything together since you're using two different cards with differing capabilities.

Since they both use the Same drivers you will not need to do anything special. Turn off your computer. Install second (slower) Video Card in the lower available ports on your Mother board. Plug your fourth Monitor into your second Video Card. Turn on your Computer and (hopefully) enjoy!

Note: I take no responsibility for your Computer becoming self-aware and/or blowing up in the process.